


petal by petal the flower of your heart

by eternalmyriadofstars



Category: Undertale (Video Game)
Genre: Alternate Universe - Underfell (Undertale), Angst, F/F, F/M, Hanahaki Disease, Hurt/Comfort, Major Illness, Multi, Pining, Romance
Language: English
Status: Completed
Published: 2021-01-02
Updated: 2021-02-06
Packaged: 2021-03-12 07:41:55
Rating: Teen And Up Audiences
Warnings: Creator Chose Not To Use Archive Warnings
Chapters: 3
Words: 11,643
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/28506888
Author URL: https://archiveofourown.org/users/eternalmyriadofstars/pseuds/eternalmyriadofstars
Summary: It started with two petals. Now dozens of flowers grow through Sans’s ribcage. He must choose to confess his blooming love to the most important women in his life and hope their returned love cures him, or remain silent and let the thorns pierce his soul. His brother won’t let him wilt so easily, but in the end, petal by petal, it may be no choice at all.
Relationships: Alphys/Sans/Undyne (Undertale), Papyrus & Sans (Undertale)
Comments: 4
Kudos: 34





	1. at the edge of a petal

**Author's Note:**

> Whew, it’s been a while since I last posted, hasn’t it? I thought this up on a whim, and it… kind of got away from me. What was supposed to be a quick one-shot turned into a three-chapter behemoth.
> 
> I adore Salphyne, but it’s sadly rare, so I figured: why not write my own?
> 
> Warnings for illness (involving coughing) and general Underfell-ness.

  
  


It started with two petals.

Sans woke up one morning to a tickle in his throat, which turned into a full-fledged cough, until he ended up with two petals in his hand. He stared, because what? He hadn’t eaten any flowers lately, at least not to his knowledge.

He turned them over in his palm, studying them. The one was broad, a bright cyan at one end slowly fading into green at the other. The other was thin at one end and broad at the other, and was a nice shade of orange.

He narrowed his eyes. Had someone slipped something into his food at Grillby’s? Maybe Papyrus was trying a new recipe and didn’t warn him? 

Or maybe it was just general magic weirdness. Wouldn’t be the first time something freaky had happened to someone down here.

Sans shrugged and shoved them into his pocket, resolved to throw them away later.

\---

He didn’t throw them away, and they didn’t stop, either. In fact, as the days wore on the whole thing grew worse, until he was coughing up flower petals several times a day. There were always at least two, and they were always the same colors: cyan-green and orange.

“Sans, are you okay?” Grillby asked as Sans coughed into the sleeve of his coat for the third time that night.

“i’m fine, grillbz,” Sans rasped, reaching for the water Grillby had placed near his elbow. “just swallowed wrong.” A tickle hit the back of his throat, and he started hacking again.

“Uh huh.” Grillby eyed his water pointedly. “Well, if you’re sure you’re alright you can...” He trailed off, gaze caught on something on the table. “Sans. What are those?”

Sans looked up blearily. “what’s what?”

Grillby reached forward and picked up two small objects. Sans caught a glimpse of them before they were engulfed in flames.

shit. Two of the petals had fallen out of his elbow.

“nothin’,” Sans said quickly, bringing a hand up to prevent any more from falling. “just...”

“How long, Sans?” Grillby interrupted.

Sans paused and stared at him. “i... i don’t... what?”

“How long have you been coughing up petals?”

“‘bout a week,” Sans said, nonplussed. “what are ya...”

“That’s not good. Not if it’s progressed this far in just a week.”

“care to explain to me just what ‘it’ is?” Sans snapped. Grillby finally looked up from where he had been examining the petals.

“What do you know about Hanahaki?”

“hana what now?”

“Guess that answers that then.” Grillby’s gaze went back to the petals. “Hanahaki Disease happens when you fall in unrequited love.”

A jolt shot through Sans. Grillby must have noticed, but mercifully he said nothing about it.

“The afflicted begins coughing up petals,” he continued. “It starts slow, one or two at a time. And then they start coughing up full flowers.”

Sans grimaced. The petals were bad enough; he was not looking forward to coughing up flowers.

“The number of different flowers corresponds directly to the number of people the person is in love with. As you can imagine, it’s usually one, but two or more is not unheard of. And the color tends to match the original color of the monster or monsters they’re pining after.”

Sans shifted uncomfortably in his seat. He’d _thought_ that shade of green looked familiar...

“It gets worse,” Grillby continued, interrupting his thoughts. “Around that time, magic will start coming up as the flowers begin to grow in your lungs and throat. Or, around the ribs and spine for you, I suppose.”

“sounds lovely,” Sans drawled. “how do they live with themselves being a bouquet of flowers?”

He had meant it as a joke, but Grillby’s voice grew somber. “They don’t.”

“what?”

“Hanahaki Disease is fatal, Sans. If you’re not loved back by the two monsters you are pining after, then you are going to die.” There was a question there, Sans knew it. _Who has your soul so thoroughly you would die for them?_

Instead of answering, Sans asked a question of his own. “then why aren’t there more monsters out there dying from flowers clogging up their lungs? how does anyone live past being a teenager?”

Grillby shrugged. “It’s actually quite rare. Only a few cases happen a decade. No one knows why; some theorize the person’s magic has to act just right for the flowers to begin growing, while others think they have to have come across some unpredictable wild magic. And of course, there are the romantics out there who believe that only the purest of love will cause Hanahaki. Would explain why it’s even rarer, nowadays.”

Sans eyed him. “just how come you know so much about this, anyway?”

“I lost a friend to it, years and years ago. He fell in love with someone, and was too afraid to tell her how he felt. And the only way to cure it is if you were loved in return.”

“great.” Sans fished out a handful of gold and laid it on the counter, pushing back the stool and standing up in one smooth motion. “welp, thanks for the history lesson, g. just put the rest on my tab, i’ll pay ya back later.” With that, he turned around and walked away.

“Sans,” Grillby called behind him. “You need to tell them.”

Sans’s steps faltered, but he picked them back up and was soon out the door and in the snow.

\---

So. Hanahaki, huh?

Sans stared down at the petals he’d just coughed up. There were two again, one cyan-green and one orange, just like before.

_The color tends to match the original color of the monster or monsters they’re pining after._

He knew exactly who these flowers belonged to. And it was just his luck, wasn’t it, that he would fall in love with two of the least available monsters in the Underground?

_the only monsters who could be worse would be the dogi, or boss,_ he thought, a little hysterically. _or asgore._

Sans snorted at the thought of what the very temperamental, very volatile King would do if he found out someone was in love with him. He would probably have them burned alive for heresy.  
Not that this was all that much better. Sans sighed, flopping back into his bare mattress with a huff.

_The only way to cure it is if you were loved in return._

Like that was ever gonna happen. Sans took one last look at the petals in his hand and dropped them on the floor.

Welp. Looked like he was dying then. Maybe he’d even get lucky and go before Papyrus found out.

\---

Sans didn’t get lucky. Somehow, that wasn’t all that surprising. The universe really did hate him sometimes.

The coughing grew worse over the next few weeks. Just like Grillby had said, it soon progressed from petals to full-blown flowers: a sword-shaped stalk with a bunch of blooms growing down one side that held the cyan-green petals, and a funny-shaped orange thing that Sans had no idea what to make of.

And of course, petals or flowers, they always, always came in pairs. One cyan-green, and one orange.

Sans noticed Papyrus giving him increasingly worried looks as his cough grew steadily worse, but as long as he didn’t see the petals, Sans could deal with his worry. He had taken to eating quickly, afraid he would have a coughing fit in the middle of the kitchen, and then hiding out in his room for the rest of the night. It was only a matter of time before Papyrus staged an intervention.

Of course, said intervention came way too soon for Sans’s taste.

It happened during dinner one night. Sans had scarfed down his food as quickly as possible, as was the usual these days, and had just risen to leave when Papyrus spoke up.

“SIT DOWN, SANS. WE NEED TO HAVE A TALK.”

Sans looked up at his brother, halfway out of his seat. “huh?”

Papyrus was staring at him, red eyelights boring into his own. “YOU HEARD ME, BROTHER. NOW SIT.”

Sans plopped back down onto the chair, dread welling up in his chest. He’d hoped to have this particular conversation a little later on.

Or, better yet, never.

But the world didn’t ever give you what you wanted, Sans was intimately familiar with that. So he could just have this little chat with Papyrus and hope he came out of it with his secret intact.

_like that’s gonna happen,_ he thought cynically. His eyelights skittered away from Papyrus’s, unable to look his brother in the eye any longer. “so, uh, what’s up boss?” he tried.

Papyrus huffed. “YOU KNOW EXACTLY WHAT IS ‘UP’,” he said. “YOU HAVE BEEN AVOIDING ME.”

“i haven’t been-”

Papyrus slammed a fist on the table, startling Sans. “YES YOU _HAVE!_ YOU HAVE BARELY EATEN IN OVER A WEEK, AND WHEN YOU ARE FINISHED YOU GO STRAIGHT UP TO YOUR ROOM! I BARELY EVEN SEE YOU ANYMORE!” There was pain in his voice, and a stab of guilt shot through Sans. He’d been so focused on keeping Papyrus from finding out he hadn’t even thought of how his behavior would affect his brother.

What kind of brother was he?

“sorry, boss,” Sans muttered, sinking down in his seat. “didn’t mean to neglect ya like that, i just…” He trailed off, ashamed.

Papyrus shook his head. “I KNOW,” he said. “I’M ONLY WORRIED.” He furrowed his brows. “AND DON’T THINK I HAVEN’T NOTICED THAT COUGH OF YOURS; YOU KNOW FULL WELL YOU CANNOT AFFORD TO GET SICK, NOT WITH YOUR H-”

A bought of sudden coughing overtook Sans, cutting Papyrus off. Papyrus half-rose out of his seat, arm extended toward Sans as if he could ease it. “SANS?”

Sans waved him off. “i’m fine,” he muttered when he had finished. A stray cough forced a few petals out between his teeth, and Sans quickly hid them in his sleeve, praying that Papyrus hadn’t noticed.

No such luck.

“SANS. WHAT ARE THOSE?”

“n-nothin’, boss.” Sans tucked his elbow against his side and stood up, accidentally knocking his chair over. “welp, thank for the food, it was great as always, i gotta-”

“SANS.” Uh oh, Sans knew that tone. That was Papyrus’s commanding voice, one rarely used on him. “DO NOT MOVE.”

Sans remained where he was, elbow still tucked against his side, as Papyrus got up and strode around the table. He stopped half a foot from Sans and held a gloved hand out.

“SHOW THEM TO ME. NOW.”

Slowly, Sans brought up his free hand and cupped it under his elbow. He cast a pleading gaze on Papyrus, who just glared at him, unmoved. Hesitantly, Sans relaxed his elbow and allowed the petals and few flowers to fall into his cupped hand. He closed a shaking a fist and brought it toward his brother’s. He paused, but opened his fist and allowed the petals to fall into Papyrus’s palm.

Papyrus took a deep breath. “HOW LONG HAS THIS BEEN GOING ON?”

Sans shifted his weight. “not long,” he muttered. “a few weeks, maybe a month?”

“AND YOU THOUGHT TO HIDE IT FROM ME?”

Sans winced at the disappointment in his brother’s voice, and nodded, ashamed. “sorry, boss.”

Papyrus brought his hand closer to his face “HANAHAKI,” he breathed.

Sans grimaced. “how the hell d’ya know what that is? i’d never heard of it before.”

“WE HAD A CASE ABOUT A YEAR AGO. THE MONSTER ENDED UP DYING FROM IT.” He tilted his hand slightly, studying the petals under the dim light. “A GLADIOLUS AND AN IRIS,” he murmured.  
Sans’s head shot up. “wait, how do ya know that?”

“I READ IT IN A BOOK I FOUND IN THE DUMP,” he said distractedly. “WHO DO THEY BELONG TO?”

Sans grinned. “you’re so cool, boss.”

“AND YOU ARE DEFLECTING. WHO IS IT, SANS.”

Sans winced. “can i not tell ya?” he pleaded.

Papyrus shot him a glare. “OF COURSE NOT, SANS! HANAHAKI IS _FATAL_.” He frowned down at the petals. “IT MUST BE TWO MONSTERS,” he said under his breath. “THE NUMBER OF FLOWERS CORRESPONDS TO THE NUMBER OF LOVERS.” Papyrus squinted. “AND THE COLOR OF THE PETALS TENDS TO MATCH THE LOVED ONE’S ORIGINAL… MAGIC… COLOR…” He trailed off. Sweat began to bead on Sans’s forehead at the calculating look on his brother’s face. He knew that look.

“UNDYNE’S SPEARS USED TO BE CYAN,” Papyrus said slowly. “AND SHE STILL USES GREEN MAGIC. ALPHYS’S MAGIC WAS ORANGE.” He looked up at Sans. “IT’S THEM, ISN’T IT.”

Sans’s eyelights skittered away from his face. “it’s who,” he protested weakly.

“DON’T PLAY STUPID WITH ME, BROTHER. YOU ARE IN LOVE WITH UNDYNE AND ALPHYS, AREN’T YOU.”

Sans was impressed, despite himself. Alphys wasn’t even really Papyrus’s friend, yet he still knew her original magic color.

“yeah,” he muttered, shoulders slumping in defeat. “it’s them.”

“OH, _SANS_ ,” Papyrus whispered, distress radiating from his tone. Sans flinched at the sound. “BOTH OF THEM?”

“i _know_ ,” Sans said, helplessly. “i know i have no chance with them, but i just… i can’t _help_ it.” His voice cracked on the end of his words, and horrifically Sans could feel tears begin to well up in his sockets. He brought up a sleeve to wipe them away before they could fall.

Fortunately, Papyrus said nothing about it. He just stared at the petals in silence for a moment, before he spoke back up. “I’M SURE THEY WILL LOVE YOU BACK.”

Sans snorted. Sure, and maybe the old lady would come out of hiding, and ol’ King Fluffyass would renounce his decree of kill or be killed and declare peace with the humans, and monsters would finally get out of this hellhole, and...

Anyway. Point was, there was no way Undyne and Alphys would just… love him back. The Underground wasn’t that kind a place.

Undyne and Alphys were already perfect together. They didn’t need a one-HP monster who had to wear his little brother’s collar just to keep from getting murdered holding them back.

He brought an arm up to grip onto the opposite side of his coat, gaze fixed firmly on the table. Stars, he must look like such a mess.

Papyrus must be so disappointed in hi-

Sans gasped as a pair of bony arms encircled him, and loosened the grip on his coat. “boss?”

“YOU NEED TO TELL THEM,” Papyrus whispered from where he had placed his chin on top of Sans’s skull. “AND SOON. BEFORE IT IS TOO LATE.”

Sans closed his eyes, bringing his own arms up to return the hug. “can’t,” he choked out.

Papyrus’s grip tightened around him. “WHY NOT?”

Sans shook his head, refusing to voice his thoughts.

“SANS?”

“scared,” Sans admitted. “there’s no way they’ll love me. they’ll either pity or hate me, and i can’t…” He trailed off, unable to finish.

Papyrus let out a shaky sigh. “PLEASE?” he asked, sounding like he already knew the answer.

“sorry, boss.”

They stood like that for several minutes, surrounded by the petals Papyrus had dropped. Finally, Papyrus let go of his brother. He quickly turned his head away, but not before Sans noticed the tell-tale red encircling his sockets. A lump formed in his throat.

Crying. He’d made his brother cry.

“WELL,” Papyrus said briskly, but the shaking in his voice betrayed him. “IF YOU ARE FINISHED WITH YOUR FOOD, YOU MAY GO UPSTAIRS. I UNDERSTAND IF YOU’D RATHER BE ALONE.”

He looked so dejected. Sans reached out and grabbed onto his brother’s sleeve. “boss,” he began, desperately. “no. i want to spend time with you. if this…” He swallowed. “if this is really it, i don’t want to spend my last days alone. can we just. watch mettaton together? please?”

Sans heard the click of Papyrus’s magical throat as he swallowed. “YES,” he said. “I WOULD LIKE THAT.”

They didn’t say anything else as they cleaned up, Papyrus washing the dishes as Sans straightened their chairs. Finally, they sat in front of the TV.

Just like old times.

“boss,” Sans said eventually, breaking through the sound of Mettaton’s self-absorbed speech.

Papyrus tilted his head toward him. “HMM?”

“don’t tell them. please.” He didn’t bother to specify who.

“SANS,” Papyrus began, voice trembling ever so slightly.

“please. i don’t know if they’ll hate me or not, and if they do i… i don’t think i’ll be able to take it. i don’t want to worry them over the hanahaki, either.”

“ALPHYS IS A DOCTOR,” Papyrus tried. “SHE CAN HELP.”

Sans chuckled mirthlessly. “she can’t do anything and you know it. _please_ , boss.”

Papyrus didn’t say anything for a moment, then, “ALRIGHT, BROTHER. BUT IF IT GETS TOO BAD, I AM TELLING THEM ABOUT THE DISEASE.”

“boss…”

“THEY DESERVE TO KNOW, SANS. THEY DESERVE TO KNOW WHY YOU’RE D- WHY YOU ARE DYING.”

Sans’s soul clenched. Dying. He was dying.

“alright,” he conceded. “if it gets too bad, we’ll tell ‘em. but not who it is. please.”

Papyrus didn’t answer.


	2. petals i may have once pursued

**Notes for the Chapter:**

> Sorry this took so long, I kept forgetting to post! Anyway, without further ado, here is the second chapter!
> 
> Warnings for illness (involving coughing) and general Underfell-ness.

Sans coughed a little in the cold air, but fortunately it seemed to be just that: a cough. No petals creeping up his throat.

For now.

He shivered as a gust of wind blew past him and shoved his hands in his coat, glancing around. Monsters milled about Snowdin, but the sight of his bright red collar and the fear of Papyrus’s retaliation kept him mostly safe these days. He was waiting outside Grillby’s for Undyne and Alphys. The three of them – or two, if one was busy – liked to meet up once a week to get lunch and chat, and he had been looking forward to this for days.

The Hanahaki had progressed slowly yet steadily since Papyrus had found out around a week ago, and while Sans was glad to be able to spend more time with his brother again, it didn’t come without its downfall. Namely, Papyrus’s increasingly distressed glances every time he coughed up a petal or ten.

Sans sighed, watching the mist blow about in the breeze. He had missed Papyrus, but hated worrying him. It reminded him too much of their childhood, when Sans had always insisted on giving Papyrus most of the food and ignored the kid’s constantly worried looks.

“Hey, Sans!”

Sans blinked out of his thoughts and turned around, hands still in his coat pockets. Undyne was jogging toward him, dressed in warm yet protective clothing. Sans smiled at the sight.

“heya, ‘dyne,” he said as she neared. “glad ya could make it.”

Undyne’s face split into a wide grin under her scarf and she clapped him on the back, nearly knocking him over with the force. “Hey, wouldn’t miss a date with one of my favorite skeletons, now would I? Come on, let’s go in; I’m starving!”

Sans followed her lead, ignoring the butterflies in his stomach at the word “date”.

_she didn’t mean it that way, it was just a phrase of speech._ Out loud, he snarked, “thought i was your favorite skeleton? don’t tell me boss is your fave.”

Undyne belted out a laugh as she opened the door to Grillby’s, causing heads to turn. The others quickly turned back around at the sight of the formidable Captain of the Royal Guard. “Hah! You know that bonehead; if he wasn’t at least equal to you, I’d never hear the end of it.”

Warmth spread through Sans’s chest at her words. _she likes me at least as much as boss,_ he thought, a little giddily.

They made a beeline toward Sans’s usual seat, Undyne sitting to his right. More warmth spread through him at the blatant display of trust. He knew she didn’t like people getting so close to her blind side, so for her to purposefully sit with her bad eye facing him…

Undyne raised a hand to rub the back of her head, interrupting his thoughts. “Sorry Alph couldn’t make it, she’s working on something.”

Sans shrugged. “it’s fine, i get how busy she can be.” Just being the Royal Scientist’s assistant had been bad enough; he didn’t even want to know how bad Alphys had it, what with Asgore’s increasing pressure to find a way to break the Barrier.

“Yeah,” Undyne muttered. She sounded off.

Sans poked her. “what’s wrong?”

Undyne blinked down at him. “Hm? Oh, nothing.”

“that don’t sound like nothin’. come on, tell ol’ sansy what’s eatin’ ya.”

Undyne snorted. “I’m older than you,” she shot back as their food arrived. Her face brightened at the burg and she took a hearty bite. Sans followed suit, knowing he likely wouldn’t get anything more out of her until she was at least half done.

Sure enough, a few minutes later Undyne swallowed a fry and spoke back up. “It’s just…” She lowered her voice. “It’s Asgore.”

“what about him?” Sans made sure to keep his voice just as low; it wouldn’t do for them to accidentally be overheard talking about the King.

“He’s been getting on Alph a lot lately, trying to find a way past the Barrier. I barely even get to see her anymore, and when I do she’s exhausted.” Her tattered fins drooped a little. “She’s not even allowed to tell me what she’s working on, and I just…”

“wish you could help?” Sans offered. Undyne nodded.

“Yeah, exactly. I just want to help my girlfriend out.”

A pang ran through Sans at her words. “Girlfriend”. He forgot, sometimes, that the two of them were dating. That there was no room in their relationship for him, no matter how close they all were.

A cough startled him out of his thoughts, and he began hacking into his elbow.

“Whoah!” A hand pounded him on the back, forcefully enough to be effective but not so much as to hurt. “Hey man, you don’t sound so good.”

Sans waved a hand at her as he finished his coughing, praying to the Angel he didn’t believe in that no petals were visible. “eh, i’m fine. just swallowed wrong.”

Undyne furrowed her brows. “If you’re sure…”

Sans stood up, tucking his elbow against his side. “yeah. anyway, i need to go home – i forgot, i was supposed to help boss with something.”

Undyne blinked up at him, startled. “But you didn’t even finish your burger!”

“not hungry, you can finish it.” He raised his voice. “hey g, put our food on my tab, ‘kay?” Ignoring Grillby’s pointed nod, Sans turned back to Undyne, shifting uncomfortably. He could feel more petals tickling their way up his throat, and suppressed another cough.

“Well, if you’re sure…” Undyne began, brows furrowed. She looked worried. Sans hated to leave her like this, but he _needed_ to get out of here before she saw the petals.

“yeah,” he muttered. “same time next week?”

“Yeah, same time,” Undyne said, sounding distracted. “Sans…”

But Sans had already turned around, and pretended not to hear. He rushed out the door, ignoring the worried gaze he could feel burning the back of his skull.

\---

Another day, another dollar, or so the human saying went.

 _the hell’s a dollar?_ Sans mused as he settled against the dull purple door at the end of the path. His breath rose in the air as he exhaled, and he imagined they were the clouds he was never gonna see. Not that he would’ve seen them in the first place, what with everyone being trapped down here for all eternity, but still. The hope had been there.

Sans grimaced at the dismal thought and rasped his knuckles against the door. “knock knock.”

Rustling came from the other side, then a voice sounded. “Who is there?”

“hal.”

“Hal who?”

A slight tickling sensation hit the back of Sans’s throat, and he suppressed a groan. _not now._

“hal ‘bout you open the door and find out?”

A beat, then the lady on the other side roared with laughter. Sans grinned. _looks like that one’s a keeper._

He was rummaging through his mind in search for another rib tickler when the scratch in his throat grew unbearable. _here it comes,_ he thought miserably, just before a series of coughs killed all thought.

“My friend?” The lady sounded alarmed, but he couldn’t focus enough to even attempt to answer her, too busy hacking up what felt like half a rib. Finally, it was over. Sans slumped back against the door, defeated.

“My friend, are you alright?”

“fi-“ Sans grimaced as a whole flower forced its way past his teeth, leaves and all, and spat it out. It was orange. An iris, then. “i’m fine.”

“My friend,” the lady began, and paused. When she spoke again, her voice was even, careful. “You do not sound fine. Forgive me for asking this, but have you... Have you ever heard of Hanahaki?”

Sans let his head fall back against the door with a thud. Did everyone in the damned Underground know the name of this stupid thing but him?

“yeah,” he muttered, voice rough. “i’ve heard of it.” He coughed, once.

“Oh, my friend,” she murmured, and her sympathy grated on his ears.

“‘m fine,” he repeated, without any heat. He was tired.

She hummed noncommittally. There was another pause, and then, “Do they know?”

“ _no,_ ” Sans ground out. He was starting to get sick of that question. “and i’d like to keep it that way, thank you very much.”

“Of course.” The silence this time was marginally more comfortable. Sans allowed himself to relax against the door.

He was nearing a light doze when she spoke back up. “Tell me about them?”

No “why not?” No pleads, demands he tell the two he was in love with them, in hopes that they might dredge up a shred of affection to save his sorry ass. Just a friend, willing to listen to him describe the loves of his life.

“well,” he began. “first off, their names are undyne and alphys. undyne’s captain of the royal guard, and alphys…”

\---

Sans was getting ready for bed when it happened. He had just taken off his coat when his throat grew scratchier than usual. He hadn’t removed any more than that since this whole thing had started, too afraid of seeing the physical manifestation of his looming death, but he could still feel abnormal lumps under his sweater and collar.

There was barely enough time for him to think, oh no, when all thoughts were forced out by the worst coughing fit yet. It felt like his ribs were being split open by the force of it, like he would burst into dust at any moment.

Rapid footsteps, barely audible over the hacking coughs, sounded outside his door.

“SANS?”

Sans opened his mouth to tell his brother that it was fine, don’t come in, but before he could so much as get a word out another series of coughs stole his breath away.

“THAT’S IT, I’M COMING IN.” Sans barely even heard the sound of the doorknob over his own wheezing breaths as he fought to get it under control.

“SANS, ARE YOU ALRI- SANS!” Papyrus raced toward Sans and dropped to his knees. “BROTHER, CAN YOU HEAR ME?”

A bark of air was his only response.

“SANS!” There was panic in Papyrus’s voice, and a jab of guilt ran through Sans at having made his brother sound like that. It was quickly smothered by him coughing up two flowers simultaneously.

“THAT’S IT, I’M CALLING DR. ALPHYS.”

“i’m f-“ Sans began, but he was interrupted by a fit that rattled his entire ribcage. Distantly, he could feel Papyrus place a soothing hand over his spine.

“YOU ARE NOT _FINE_ , SANS! YOU ARE ONLY GETTING WORSE!” Papyrus began to rub up and down, as if he could knead away this illness. Sans wanted to tell him it was no use, to save his energy, but all he could get out were horrible choking noises.

“SHH. SAVE YOUR BREATH.” Papyrus’s voice was soft now, comforting. “THAT’S IT, JUST LIKE THAT. EASY NOW.”

Papyrus continued to murmur soothing nothings as Sans’s coughing fit finally died down, and Sans leaned against his brother, exhausted.

“I AM CALLING HER.” Papyrus’s tone brooked no argument, not that Sans had any energy left to do so with. That fit had sapped everything he had left, leaving him weak and shaky. Each breath he took trembled like he’d just fought off an entire horde of monsters, and his throat felt like he’d been gargling glass. All around them lay a pile of gladioluses and irises in a pool of sickly red magic, like some macabre painting. The magic was staining both their clothes.

_this is gonna be hell to get out of my collar_ , Sans thought. He heard the beeping of buttons announcing Papyrus calling Alphys, and then the ringing of the dial tone. It stopped after the fifth ring.

“ _Papyrus, what the hell? It’s one o’clock in the fucking morning!_ ”

That wasn’t Alphys. Sans huffed out a laugh that he immediately regretted, pain lancing through his sternum.

“HUSH YOU,” Papyrus muttered to him, and turned back to the phone. “UNDYNE, I NEED TO SPEAK TO DR. ALPHYS.”

“ _And it can’t wait ’til morning?_ ”

Papyrus ignored the obvious non sequitur of how technically it was morning, a sign of just how rattled he was.

_heh. rattled._ Sans might be getting delirious. His head rolled against Papyrus’s shoulder, and his brother brought up a hand to gently cup the back of his skull.

“NO, IT CANNOT. THIS IS AN EMERGENCY.”

“ _And what sort of ‘oh-so-important’ emergency can’t wait until a halfway decent hour?_ ”

“IT’S SANS.”

Silence, then a sharp intake of breath could be heard over the phone.

Papyrus pitched his voice lower, as if he could will Undyne to listen. “PLEASE, UNDYNE. SANS IS VERY ILL. I NEED TO SPEAK WITH DR. ALPHYS.”

“ _I’ll get her, hold on._ ” Gone was her groggy anger, and in its place was worry and borderline panic.

_see boss,,/em > Sans thought blearily. _this is why i didn’t wanna tell ‘em. don’t wanna make ‘em worry.__

“HUSH, SANS.” Papyrus’s hand stroked his skull.

Oh. Had he said that out loud? Another cough shook through his chest, forcing a few stray petals out between his teeth. He whined. “hurts,” he gasped. The hand stroking him tightened briefly.

“I KNOW. JUST HANG ON.”

“ _Was that him? The hell’s wrong?_ ” Undyne again, this time followed by the patter of bare feet. Papyrus brought the phone back up to his ear.

“YES, THAT WAS HIM. HE IS FINE NOW.”

“Fine _? That didn’t_ sound _fine, Papyrus!_ ”

Uh oh, Undyne sounded angry. Sans opened his mouth to warn Papyrus not to piss her off further, but another cough interrupted him.

“EASY, BROTHER.”

“ _Was th-that him?_ ” It was Alphys this time. She sounded worried, but was being too professional to show it beyond a worse than usual stutter.

“YES. AND HE IS FINE NOW; IT WAS FAR WORSE EARLIER.”

“ _It was_ w-worse _? You had better b-bring him in, r-right away! I’ll set up some t-tests, see if we c-can’t figure out what’s c-causing this-_ ”

“NO NEED. I KNOW EXACTLY WHAT IT IS.”

There was a pause, and then, “ _And ya didn’t think to bring him in_ before _now?_ ”

Sans winced, despite himself. Undyne had passed pissed, and sounded downright furious now. He could picture her standing in Alphys’s lab, hair in disarray and minus an eyepatch, glaring at the phone like she could set Papyrus on fire through it by sheer force of will.

“ _Wh-what is it?_ ” Alphys asked, interrupting his thoughts.

“HANAHAKI.”

Silence. It was broken by Alphys’s sharp sob.

Sans’s soul throbbed at the sheer pain in her voice. He raised his head and looked at the phone. “it’s okay, alph,” he said weakly. “‘m fine. i-” Another cough cut him off, and Papyrus braced him with his arm.

“QUIET, SANS! YOU’LL SET IT OFF AGAIN!” The panic was back in his voice at the thought of another coughing fit like the last one. Sans couldn’t blame him; he honestly wasn’t sure he could survive another, not so soon after the first.

_is this how i die?_

“ _Alph? Alph, what is it, what’s Hanahaki?_ ” The alarm that had laced Undyne’s voice ever since Papyrus had uttered Sans’s name was full-fledged now.

Alphys didn’t answer, or maybe she couldn’t. Papyrus did so for her, explaining in a calm voice that belied his shaking what Hanahaki was and how it was fatal.

Alphys let out another sob.

“ _Fatal?_ ” Undyne’s voice was unnaturally quiet, and there was pain there, too. Sans’s soul gave another little throb at the sound of it.

Papyrus rattled out a sigh. “YES. UNLESS HE IS LOVED BACK BY THE MONSTERS-“

“ _Wait, ‘monsters’? As in more than one?_ ”

Papyrus winced. “YES. THERE ARE TWO FLOWERS.”

A beat, then a bark of watery laughter. “ _You never do things by halves, do ya, Sans?_ ”

Sans huffed out a weak laugh. She didn’t even know the half of it.

Heh. Sans coughed once again, choking on a clump of petals. Ouch.

Papyrus’s hand had moved to the base of his skull and was now stroking up and down his neck, sharpened phalanges dipping just under his collar and then moving back up again. It felt nice. Peaceful.

Maybe it wouldn’t be so bad, dying like this. At least he was in the arms of his brother, surrounded by the voices of the two monsters he was in love with.

Before Sans could do something stupid like accidentally voice this thought, Alphys spoke again. Her voice sounded choked up, watery. Sans didn’t like hearing her like that. “ _H-has he told them yet? The m-monsters, I mean._ ”

“NO, HE REFUSES TO. AND I CAN’T CONVINCE HIM OTHERWISE.” The hand on Sans’s neck tightened its grip slightly, as if in admonishment.

“ _What?_ ” Undyne shouted, voice loud even through the phone. “ _Why the hell not, Sans?_ ”

“BECAUSE HE IS AFRAID.” Papyrus sounded frustrated, and another pang of guilt shot through Sans. “HE WOULD RATHER DIE THAN RISK THEM HATING HIM.”

Alphys let out a shrill whine that cut Sans straight through the core.

_please, alph. don’t sound like that. not for me._

“Sans...” Undyne muttered, sounding shocked. Papyrus’s grip on his neck had tightened to almost painful, and Sans could hear Alphys’s shaky breaths as she struggled not to cry again.

Oh. He’d said that out loud again, hadn’t he?

Papyrus swallowed. “ANYWAY,” he said, voice trembling slightly. “MAY I BRING HIM IN?”

“ _What? Of course, Papyrus!_ ” Undyne still sounded shocked, but she had pulled together quickly. Just one of the many things Sans admired about her. “ _You’d better come in now, the less monsters who see him like this the better._ ”

“OF COURSE. I WILL SEE YOU SOON.” Papyrus tapped his phone, which beeped as the line cut off. He turned to Sans and removed his hand. “GET UP, BROTHER. WE ARE GOING TO DR. ALPHYS’S.”

Sans whined at the loss of contact. He tried to stand, but his legs were shaking so hard he could hear the bones rattling. “can’t,” he gasped.

Papyrus huffed. “OF COURSE NOT,” he murmured. “LAZYBONES.” But his voice was fond, his touch gentle as he picked Sans up. “COME, BROTHER,” he said as he made his way across Sans’s room to the door. “LET US GO SEE DR. ALPHYS.”

\---

They made their way through Snowdin without incident. The only ones out at this time of night were the Dogi, and they were currently on duty on the other side of Snowdin.

Sans coughed weakly within his brother’s arms. Fortunately, it seemed the worst part was over, but over the weeks the disease had built up to a steady stream of coughs and petals.

Papyrus’s arms tightened around him, but he said nothing. Sans was grateful. He didn’t think he could hold on a full conversation right now. Besides, call him selfish, but he didn’t want to hear the worry in his brother’s voice at the moment.

Papyrus made short work of the trip to the Riverperson’s station, and they arrived in no time. The Riverperson was already there, as if in anticipation of their arrival.

“HOTLAND, PLEASE,” Papyrus said shortly as he paid the mysterious monster and stepped onto the boat. “AND MAKE IT QUICK.”

Sans knew his brother hated the thought of anyone seeing him in this state, even the strangely peaceful river guide. But this was the quickest way to Hotland, and would minimize contact with other, less amicable monsters.

The Riverperson said nothing, but pushed off the shore with their long pole and set a course to Hotland. The river seemed swifter to Sans than usual, as if it was hurrying them along. Or maybe he was just getting delirious again.

“Tra la la,” the Riverperson said out of nowhere. Sans jumped at the noise, then spasmed as another rattling cough shook through his core. “The love we feel is there for a reason. Listen to your soul.”

“AND WHAT EXACTLY IS THAT SUPPOSED TO MEAN,” Papyrus grumbled, running a soothing hand over Sans’s chest.

They didn’t answer.

Sans spent the rest of the short trip alternating between bone-deep coughs and snatches of a light doze. Finally, the boat stopped. Sans raised his head drowsily. “wha’?”

Papyrus gently pushed Sans’s head back down against his shoulder. “HUSH, BROTHER. WE ARE HERE.”

Sans nodded and closed his eyes, trying to get more comfortable. Skeletons weren’t exactly cushy, but Papyrus had taken off his armor earlier in the evening, and was wearing a dark turtleneck that felt really nice against Sans’s tired bones.

The rocking of the boat soon turned into the less-gentle rocking of Papyrus’s strides. Papyrus walked smoothly, keeping the jostling to the minimum, for which Sans was grateful. Still, every step sent a jolt through his chest, which... probably wasn’t good, now that he thought about it.

Before he knew it, they had arrived at the lab. Undyne must have been waiting because she opened the doors right away and waved them inside. “Quick, before someone sees,” she said. She closed the door as soon as they were inside and locked it.

Papyrus carried Sans over to where Alphys was beckoning them with a clawed hand. “P-put him here,” she said, pointing to the ragged blue couch. “S-sorry I don’t have a proper b-bed.”

“IT’S FINE,” Papyrus assured her, carefully placing Sans down. Sans grunted as he was jostled, and let loose another cough.

“Shit, that doesn’t sound good,” Undyne muttered, hurrying over to Sans’s side. “How’re ya feeling?”

“fine,” Sans gritted out.

Undyne snorted. “Yeah, I’m starting to really hate that word.” She turned to Alphys, who had scurried over to her work table. “Alph?”

“H-hang on,” she said, rooting around for something. Sans watched blearily as she knocked over a pile of papers and eventually extracted a small machine. Sans had no idea what it was for.

“Aha, h-here!” Alphys hurried over to the couch and ducked between Papyrus and Undyne. She held the machine up to Sans and began pressing buttons.

“wha’s tha’ do?” Sans mumbled, curious despite himself.

Alphys shot him a stern look over the machine. “Hush, Sans,” she admonished. “D-don’t talk.”

Sans huffed at her, which turned into another cough. Papyrus reached over and placed a hand on his chest again. “LISTEN TO DR. ALPHYS, BROTHER,” he scolded.

Alphys nodded at Papyrus. “Th-thank you, Papyrus,” she said. “A-alright, Sans. I’m g-going to measure your s-soul now. It’ll feel l-like a really invasive Ch-check, but it won’t t-take too long.”

She pressed something on the machine, which whirred to life. Sans squirmed as the magic washed over him.

“ugh,” he muttered when it was over.

Alphys nodded distractedly. “S-sorry,” she said, then frowned at whatever she saw there. “Th-that’s not good,” she said under her breath.

Undyne perked up. “What is it, what’s not good? Babe?”

Alphys shook her head and looked back up at Sans. “You r-really should have come in s-sooner,” she said, tone full of reproach. “You l-let it get way too bad.” She turned her glare to Papyrus. “And y-you-”

“alph,” Sans rasped, raising a weak hand. “don’t. not his fault.”

Alphys glanced back down at him, and then let out a weary sigh. Her tail, which had been stiffly raised, dropped to the ground.

“I know,” she said. “S-sorry, Papyrus.”

“IT IS ALRIGHT, DOCTOR. WHAT CAN YOU DO FOR HIM?”

Alphys frowned down at her machine. “W-well, the nature of the disease is unlike a-any monsters have c-come across before. I-”

Undyne stepped forward and placed a hand on her shoulder. “Monster, babe. What do ya mean by that?”

Alphys lowered her gaze. “I c-can ease the symptoms, but I c-can’t do anything for the Hanahaki itself.” Her head frills drooped.

“What do ya mean?” Undyne exclaimed. “You’re... You’re _Alphys!_ You can do _anything!_ ”

But Alphys was already shaking her head. “Th-there’s no known cure f-for Hanahaki,” she said. “The m-monsters he’s in love with would have to love him b-back. Not only th-that, but he would have to be m-made aware. It doesn’t work if they j-just quietly return it without him knowing. And since he won’t c-confess...” She trailed off, helplessly.

Undyne’s gills drooped. A jolt went through Sans at the sight. “Dammit, Sans,” she muttered, glancing over at him. “Why do you always have to make things so _difficult?_ ” She sounded like she was going to cry. Sans had never, ever heard her sound like that.

He didn’t like it.

“undyne...” Sans whispered, but trailed off. There was nothing he could say to make this better, not for any of them.

He was dying. And there was nothing anyone could do about it.


	3. half in love with easeful death

**Notes for the Chapter:**

> Here is the third and final chapter! Thank you for sticking with me, even with my wonky update schedule.
> 
> Warnings for illness (involving coughing) and general Underfell-ness.

None of them slept that night, too afraid Sans would fall into another horrible fit. Alphys wanted to keep him overnight for observation, despite his weak protests, and Papyrus was reluctant to leave his brother alone.

Undyne seemed to have been filled with a strange manic energy, bouncing back and forth between making coffee for everyone but Sans and hovering by his bedside. If it were any other monster in any other situation, Sans would have found it almost annoying; but as it was, he just found it borderline heartbreaking.

The mighty Undyne, reduced to errand girl. Something in Sans’s soul railed at the thought.

As the night progressed, she seemed to grow more and more agitated until it all came to a head around what passed for sunrise in the Underground. “Argh, I can’t take it anymore!” She whirled around and pointed a trembling finger at Sans. “You, shirt off, now!”

Alphys started coughing from her spot in front of her computer. Sans just blinked up at her in a daze. “what?”

“You heard me! Take your shirt off!”

“UNDYNE!” Papyrus protested, sounding scandalized. “THAT IS HIGHLY INAPPROPRIATE!”

“I don’t freakin’ care! I wanna see those damn flowers!”

Sans tensed. “undyne,” he began, and started coughing again.

“BROTHER!” Papyrus rushed to his side and crouched down to help Sans through his fit. Mercifully, it was short; when it was over Papyrus turned a reproachful glare on Undyne. “WAS THAT REALLY NECESSARY?” he snapped, rubbing a calming hand down Sans’s back.

She crossed her arms and returned the glare. “Papyrus, we need to see what we’re dealing with. We need to know how long he’s got before-” She cut herself off, but the unsaid words hung, heavy, in the air.

_Before he dies._

Before Papyrus could open his mouth to retort, Alphys scurried between them. “Undyne has a good p-point,” she said, fiddling with the edge of her lab coat. “It would be useful to s-see how far the disease has p-progressed.” She adjusted her glasses with her opposite hand and turned her attention on Sans. “M-may I?”

Sans hesitated. He had purposefully avoided removing his turtleneck for that very reason: he didn’t want to see how bad it had actually gotten. That would only make this whole thing more real, more final.

”S-Sans?”

Then again, it didn’t make any difference. He was still dying, and burying his head in the snow wouldn’t make that go away. Besides, Papyrus had had a point, all those days ago. They deserved to know.

Slowly, hesitantly, Sans nodded his consent. “alright,” he whispered, screwing his eyes shut. He didn’t want to see.

Alphys was careful as she removed his sweater, her hands steady and practiced. All the while, Papyrus kept a steady hand on his back, as if to ground him.

Three separate gasps sounded as the sweater lifted over his sternum, and Alphys’s hands grew suddenly shaky. The hand on his back began to tremble.

“Sans,” Undyne breathed, startling him into opening his eyes to the sight of three equally horrified expressions. Slowly he looked down at his chest, and immediately wished he hadn’t. There were flowers growing in his ribcage, actual honest-to-Angel flowers. They started at his floating ribs and bloomed upwards and outwards like some grotesque bouquet.

A horrible keening filled the air. It took Sans a moment to realize the sound was coming from himself.

“boss,” he gasped out. His voice sounded like it was coming from underwater.

The hand was removed from his back, and Sans’s vision swam.

“ _boss._ ”

“HUSH, BROTHER,” came Papyrus’s voice as the hand brought itself up to the top of his skull and pulled him into a warm embrace. “I AM HERE.”

Sans clung to his brother’s sweater with all the strength he could muster and finally allowed himself to break down into heaving sobs.

\---

Awareness came to Sans slowly, as if through a thick fog. First came the all-encompassing warmth, spreading out over his body as if he had been covered in a thick blanket. Despite being a skeleton, he could in fact feel the cold; being warm for once was a nice change.

Next, he could feel a bony yet comfortable form beneath his head and upper torso. Strong arms cradled him against the soft yet firm mass, and it took Sans an embarrassing amount of time to realize it was his brother holding him. Still, he was too out of it to muster up the appropriate indignation at being held like a child.

There was a pleasant rumble beneath his skull, like the purring of that old cat Papyrus used to own. Sans released a soft sigh as contentment washed through him.

The rumbling stopped. One of the arms moved off of Sans, and he scrunched his eyebrows. _bad pillow,_ he thought groggily. _stop moving._

The hand came up to rest on top of his skull and began to trace idle circles across the bone. Sans relaxed further into his brother’s hold.

The rumble started up again, and with it Sans could begin to make out the sound of voices.

“-wake him?” It sounded like Undyne, although she was never this quiet and mellow.

“N-no, let him sleep for a while l-longer.” That was Alphys.

The rumble grew stronger as Papyrus spoke up. “AS I WAS SAYING,” he said, his voice unusually low. “WHAT CAN YOU DO FOR HIS CONDITION?”

Shuffling sounded. “I-I can give him something for his c-cough,” Alphys began. “B-but really the only thing we can do is m-monitor him.”

Papyrus exhaled slowly. Sans’s head sank with the movement. “AND WHAT ABOUT WHEN IT BECOMES TOO MUCH?”

“W-well, any other illness and I’d say bring him h-here when it gets too bad, b-but with Hanahaki…” She paused. “I don’t th-think he should remain apart from you for too l-long. Not when you two have limited t-time together.”

The arm around Sans’s back tightened minutely. “I SEE.”

More shuffling. It sounded like something metal being moved. “I would b-bring him back about once a week for n-now, maybe more when it gets really b-bad.”

A shift of fabric sounded above Sans. “OF COURSE, DOCTOR. REALLY, I CANNOT THANK YOU ENOUGH.”

“Of c-course! He’s our friend; of course we’d h-help him!”

“YES. FRIENDS.” There was a melancholy tone to Papyrus’s voice. Sans didn’t like it. Sleepily, he started a rumble in his own chest; stilted, but there.

Papyrus tightened his hold again as Sans fell back into slumber.

\---

The next time Sans woke up, it was to the gentle scritch-scratch of Papyrus’s claws against his skull and the low murmur of voices as Undyne and Alphys talked.

Sans shifted. The voices stopped.

“BROTHER?” came Papyrus’s voice from above him. “ARE YOU AWAKE?”

Sans stirred his head and opened his eyes, blinking at the harsh light of the lab. “wha’?” he slurred.

Undyne grinned from her spot in Alphys’s chair. “Hey, sleepybones,” she greeted. “How’re ya feeling?”

“how-” A jaw-cracking yawn interrupted Sans’s question as he struggled to sit up. Papyrus moved to support him as he levered himself upright against the back of the couch. “how long was i out?”

“A-about an hour,” Alphys piped up from where she was sitting in Undyne’s lap. A pang ran through Sans at the sight of them, and he averted his eyes. No need to trigger another fit.

“right,” he said, shifting slightly. Suddenly he wanted to be anywhere but here. “so, uh, am i okay to go home now?”

Alphys hopped off the chair and made her way over to her desk. She came back a moment later holding a small bottle. “This should help with your c-cough,” she explained, handing it over. Inside were several tiny white pills. “Take one when you f-feel one coming on, it should m-mitigate it.”

Sans shot her a small but genuine smile. “thanks, alph.”

She nodded. “Of c-course, Sans. We’re h-here for you.”

“Yeah, punk. Don’t be afraid to come to us if you need help, okay?” Undyne added.

Sans opened his mouth to protest – like hell he was going to bother either of them with his issues – but Papyrus cut him off. “I WILL SEE TO IT THAT HE DOES. THANK YOU, UNDYNE, DOCTOR.”  
Sans shot his brother a baleful glare but allowed himself to be ushered out the door and into the heat.

\---

The next week passed by slowly. Papyrus and Undyne had taken Sans off of sentry duty. “TO MAKE SURE YOU DON’T FALL EVEN MORE ILL,” as Papyrus put it.

Sans had never thought he’d miss sitting out in the snow and staring at nothing all day.

To make matters worse, he was completely housebound. Papyrus would stop in to check on him periodically throughout the day, which meant Sans couldn’t sneak out to visit the lady behind the door, or Grillby’s, for that matter.

_she’s gonna be so pissed at me,_ he thought one afternoon as he was browsing through the tv. _let’s see here… mettaton cooks, mettaton dances, mettaton tells the news… oh look, mettaton terrorizes monsters with a chainsaw. fascinating._

He allowed his head to flop against the back of the couch with a groan that echoed in the empty house.

_so. bored._

Stupid Papyrus, not allowing him out of the house. Stupid Undyne and Alphys, for backing him up.

But no, that wasn’t fair; they were just trying to help. Besides, with Sans’s usual lazy attitude, he should be having the time of his life right now. Still, there was a difference between being lazy and being completely inactive, and right now Sans was smack-dab in the territory of the latter.

The sound of the door unlocking had Sans picking his head off the couch, just in time to see his brother come in. He watched lazily as Papyrus locked the deadbolts behind him and reached down to remove his boots.

“done with patrol?” Sans drawled.

“YES,” Papyrus said, not looking up from where he was unbuckling a boot.

“cool.” Sans yawned. Man, who knew doing nothing was such tiring work?

Boots off and straightened neatly against the wall, Papyrus straightened up to his still-towering height. “AND YOU, BROTHER? HOW WAS YOUR DAY?”

Sans shrugged. “oh, you know, the usual. took a nap, watched some mtt, took another nap.”

Papyrus put his hands on his hips. “YES, WELL, YOU COULD HAVE AT LEAST CLEANED YOUR ROOM BETWEEN NAPS.”

Sans shot him a cheeky grin. “nah, i’m not that bored.”

Papyrus rolled his eyes and strode toward the kitchen. Sans forced himself to his feet and strolled after him, sitting down at the table and watching through half-lidded eyes as his brother bustled around. Halfway through watching Papyrus boil the lasagna, a thought came to Sans. “hey boss, wanted to ask you something.”

Papyrus looked over at him. “HMM? WHAT IS IT?”

Sans drummed his fingers on the table. “wanted to ask if you mind if i go to grillby’s tomorrow. it’s my usual lunch day with undyne and alphys, and they didn’t want me to wander outside of snowdin.”

Papyrus furrowed his eyebrows. “I’M NOT SO SURE I AM COMFORTABLE WITH YOU GOING TO GRILLBY’S,” he said. “IF SOMETHING WERE TO HAPPEN… IF YOU WERE TO GO INTO ANOTHER FIT…”

“come on,” Sans pleaded. “i haven’t been out of the house in days. i’m starting to go stir-crazy. ‘sides, ‘dyne and alph’ll be there in case something does happen.”

“BROTHER…”

“please, boss? i haven’t missed a lunch yet, and i don’t want to start now. especially given the circumstances.”

Papyrus’s eyes softened. “YOU WISH TO SPEND TIME WITH THEM. VERY WELL, BROTHER. I WILL NOT STOP YOU. BUT I WANT YOU TO BE CAREFUL.”

Sans grinned his thanks. “i will, don’t worry about me.”

Papyrus snorted. “EASIER SAID THAN DONE, DEAR BROTHER.”

\---

Sans shivered lightly as he waited for Undyne and Alphys to arrive. It had begun snowing that morning, and hadn’t let up since. In fact, it seemed to be coming down even harder, fat flakes blowing at a slight diagonal in the slight breeze.

So much for no weather underground.

He perked up a little at the sight of a tall, blue figure walking toward him and raised a hand in a wave. “heya!”

Undyne came to a stop in front of him and furrowed her eyebrows. “You sure you should be out in this weather?”

Sans rolled his eyes. “it’s _snow,_ in _snowdin,_ that’s what it _does_ here. it’s not like there’s a blizzard or anything.”

That concerned look didn’t let up. “Still…”

A spark of irritation shot through Sans. He was so sick of everyone treating him like he was made of glass! “well, if you don’t want to get something, i’m going in alone.” With that, he whirled around and started to march toward Grillby’s.

A hand on his arm stopped him. “Wait.”

He turned around. “what,” he snapped.

Undyne’s fins drooped slightly as she gazed down at him. “I’m sorry,” she murmured. “I didn’t mean to upset you, I just…” She dropped her voice to a near whisper. “You’re _dying,_ Sans. I don’t want it to happen any faster than it is already!”

Sans winced at the hurt in her voice and dropped his hands to his pockets. “sorry,” he muttered, glancing away. It was too difficult to look at the pain on her face. “didn’t mean to snap, i’m just… He brought his free hand up to rub over his face and let out a bone-deep sigh. “frustrated. boss won’t let me do _anything_ anymore, and while normally i like to take it easy, this is just… too much, ya know?”

The hand moved up to his shoulder. “I _do_ know. When I lost my eye, Gerson made me stay at his place for weeks. Wouldn’t let me do anything. I understand it’s frustrating, but this isn’t just a missing eye. You’re _dying._ And I can’t blame your brother for wanting to stop that.”

Sans tensed under her grip. He could almost hear the unasked question. _Why won’t you do anything about it?_

If only she knew.

Silence fell like snow between them. Sans cleared his throat to break it. “so, uh, is alph gonna make it this week?”

Undyne removed her hand, fortunately saying nothing about the obvious subject change. “Yeah, she should be here soon.”

Sans nodded. “good. asgore still raggin’ on her?”

Undyne groaned. “ _Yes!_ I’m about ready to march in there and make him stop, King or no!”

That startled a laugh out of him. “yeah, and get burnt to a crisp. what should i spread your dust on?” he teased. “your spears?”

Undyne grinned. “Oh, a bit of this, a bit of that. Don’t forget my anime!”

Sans snorted and opened his mouth to reply, only to be interrupted by a voice.

“H-hey guys, sorry I’m l-late.”

Sans turned to see Alphys jogging toward them, bundled up in a pretty maroon coat that contrasted nicely with her scales. He smiled at the sight. “heya, alph.”

“Hey babe!” Undyne crowed, and whistled. “You look good in that!”

Alphys blushed. “Th-thanks,” she said. Turning to Sans, she furrowed her brows. “Sans, should you really be out in th-this weather?”

Sans groaned. “not you too. i’m _fine._ can’t even feel the cold, goes straight through me.” He winked.

Alphys huffed. “That’s a l-lie and you know it, Sans.”

Sans winced. He turned to Undyne for help, but paused as he noticed her watching him intently.

“So you skeletons _can_ feel the cold,” she mused. “I’d wondered about that.” She narrowed her eyes, and with a firm nod she rose her hands to the scarf around her neck.

“yeah? i don’t-” Sans cut himself off as Undyne unwound her scarf, and froze as she reached toward him. “wha-”

“Here,” she said. Sans stood there, stunned, as she began to wrap it around his neck and lower jaw. “There!” She finished by tucking the end under his chin. “Now you’re warm.”

“th-thanks,” Sans stuttered. He glanced over at Alphys to see her watching the two of them intently. A blush rose on his cheekbones and he quickly looked away.

_idiot._

“so, uh, should we go inside?” He jerked a thumb toward the door.

_of course she’s staring at you. you just got intimate with her girlfriend!_

“Y-yeah,” Alphys said. “I’m starving.”

By the time they got their food and started eating, Sans’s discomfort was all but gone. Still, he couldn’t help but bury his face a little in the warm scarf from time to time.

It smelled like water and metal.

Undyne and Alphys didn’t bring up his condition again, likely too afraid someone would overhear and use the knowledge against him. But when they got ready to leave, Undyne refused to take the scarf back.

“Keep it,” she said with a small smile. “You need it more than I do.” With that, she and Alphys turned back toward Waterfall, leaving a furiously blushing Sans staring after them.

Still, he didn’t take the scarf off for the rest of the day.

\---

Sans regretted his little outing the next day. He woke up to a coughing fit that shook his entire body.

Footsteps sounded outside his room. “SANS?” Papyrus called. “I’M COMING IN.”

The door creaked open, and Papyrus hurried to his bedside. Sans struggled to sit up, and sighed in relief as a gloved hand helped him lean against the wall. “thanks,” he forced out.

“HUSH, BROTHER, AND TAKE THIS.” Papyrus handed him a pill and a glass of water, which Sans accepted with relief.

It took a few minutes, but finally the fit died down. “alph’s an angel,” Sans muttered once he was confident he could speak again. He looked up at his brother, who was watching him with furrowed brows.

Uh oh.

“boss,” Sans began, but cut himself off when Papyrus held up a hand.

“YOU CANNOT TELL ME IT IS COINCIDENCE THAT THIS HAPPENED THE DAY AFTER YOUR LUNCH WITH UNDYNE AND ALPHYS,” he said sternly.

“yeah, but-”

“NO BUTS, SANS. I DO NOT WANT THIS TO HAPPEN AGAIN. NO MORE LUNCHES WITH THEM.”

Sans’s jaw dropped open. “ya can’t just _do_ that, boss!”

Papyrus crossed his arms. “I CAN AND I WILL. AND IF I CALL UNDYNE AND LET HER KNOW WHAT HAS HAPPENED…” He trailed off, pointedly.

Sans flinched. “boss, don’t, _please_. she might guess, and i can’t…”

Papyrus’s expression softened. “I WON’T, BROTHER. BUT I DON’T WANT YOU GOING TO ANY MORE LUNCH MEETINGS.”

“but that’s the only time i get to see them,” Sans all but begged. “ _please._ just one more week. i want to tell them myself.”

Sans could see Papyrus visibly fighting with himself. Finally, he broke down with a huff. “FINE. ONE MORE WEEK.”

Sans smiled. “thanks, boss.”

\---

Sans never did get to meet up with them. Two days later, he ran out of medication.

“ALRIGHT, BROTHER,” Papyrus said. “WE ARE GOING BACK TO DR. ALPHYS’S.”

Sans groaned from his spot on the couch. “do we have to? i’m fine, boss. haven’t had a fit all day.”

“AND YET THEY ARE COMING MORE AND MORE FREQUENTLY,” Papyrus said. “BESIDES, YOU COULD DO WITH A CHECK UP. WE ARE GOING.”

Sans grumbled but rolled off the couch anyway. He crammed his feet into his shoes and followed his brother out the door.

The trip to Hotland was a lot less stressful this time, for both of them. When they had made it to Alphys’s lab, Papyrus spoke up. “HONESTLY, BROTHER,” he said as he rapped on the door. “I WOULD HAVE THOUGHT YOU’D JUMP AT THE CHANCE TO SEE HER AGAIN.”

The door opening saved Sans from having to answer. Undyne stood in front of them, dressed in a tank top and shorts.

“Hey, punks!” she greeted. “Come on in, Alph’ll be here in a sec. So, what’re ya here for?”

“SANS HAS RUN OUT OF HIS MEDICATION,” Papyrus said. “WE ARE HERE TO PICK MORE UP.”

Undyne nodded. “I think Alph said she’s got more, if you need it.” She raised her voice. “Hey Alph! Sans and Pap are here, they need more meds!”

“I’m c-coming!” came Alphys’s voice from upstairs. Sans watched, amused, as she practically ran down the escalator.

“ya know, there’s a reason those things move,” he drawled. She shot him a look.

“Oh, ha ha,” she said. “Undyne said you need more m-meds?”

Sans rolled his eyes. “boss is just being overprotective, i’m _fine._ ”

Alphys snorted and bustled over to her desk.

Sans noticed that Undyne hadn’t taken her eyes off him since he’d gotten there. He raised a brow at her. “what?”

She just hummed and turned her attention to Papyrus. “Hey, Paps,” she said. “I left my pajamas at home, do you mind running to get them for me?”

Papyrus scowled at her. “CAN’T YOU GET THEM YOURSELF?” he grumbled, crossing his arms.

Undyne smirked. “Nope.”

Papyrus rolled his eyes but started walking toward the door anyway. “FINE, FINE. NEVER SAY THE GREAT AND TERRIBLE PAPYRUS DOESN’T DO FAVORS FOR A FRIEND.”

“Thanks!” she called after him, earning a slam of the door in response.

Sans blinked at the exchange. Weird. With a dramatic sigh, he plopped onto the ground in the middle of the floor. “man, i’m beat. didn’t sleep much last night.”

“The cough that bad, huh?” Undyne asked, taking a seat beside him.

“yeah.”

They sat in silence for a few minutes before Undyne turned to him, expression serious. “Sans, I never asked. Who are those flowers for?”

Sans shifted uncomfortably. “doesn’t matter,” he muttered. “they wouldn’t love me back anyway.”

She scooted closer to him, causing his breath to hitch. “And if they did?”

“they won’t.”

Closer still. Sans’s mind ground to a halt.

“Then what if it were someone else?”

Sans chuckled nervously. “heh, heh, what are ya-”

“I’m going to kiss you now, Sans,” Undyne interrupted.

Sans’s soul stuttered. What? He gaped at her.

She just gazed back at him, expression soft. “If you don’t want me to, just say so. We don’t ever have to speak of this again.”

“ _no,_ ” Sans said in a rush. “i mean-” He took a shaky breath to calm his suddenly racing soul. “i would like that.”

Undyne’s face split into the widest grin he’d ever seen from her, and without another word she leaned forward. Sans had just enough time to think, _alphys is gonna be so mad_ before she pressed her lips to his teeth and all thought fled from his mind.

The kiss was chaste, yet sent a shock of electricity down his spine. Sans’s eyes fluttered closed as Undyne’s hands went to his face, cupping his cheekbones, and he flailed his own arms for a moment before one hand went up to her ponytail and the other clung to her shoulder like a lifeline. Her lips were smooth and soft, with the slightest hint of scales.

She smelled like metal and water.

A squeak from Sans’s right drew him out of his daze, and he broke off the kiss with a gasp. Undyne grinned down at him. “You’re a natural.”

Sans’s eyes widened. He’d just kissed _Undyne!_ His eyelights skittered over to Alphys, fully expecting a death glare.

But what he found wasn’t a glare at all. Instead, she was watching him very, very intently, with a slight blush on her cheeks.

Had- had she _enjoyed_ it?

Sans opened his mouth to ask, but Undyne beat him to it. “Your turn, babe!”

Before Sans could ask what the hell that meant, Alphys had dropped to his side and placed a hand on his cheekbone. “My turn,” she said, without a hint of a stutter.

And then she was kissing him.

Another electric shock shot down Sans’s spine. Alphys’s lips were rougher than Undyne’s, but no less pleasant. Her hand was smaller as well. Sans allowed his own to go to her hip, the other caught by one of Undyne’s. He had no idea when that had happened.

Alphys smelled different, too, metal and coffee and the slightest hint of ozone. Her lips moved slightly against Sans’s teeth, and he couldn’t help but gasp. She kept her lips pressed against him for another second before drawing back slowly.

Undyne whistled. “Damn, that was hot!”

Heat rose to Sans’s cheeks, and he wished he’d thought to put on Undyne’s scarf before coming here. He took a moment to be thankful Papyrus wasn’t in the room before the worst fit yet came on, and all thought fled his mind.

Pain shot through his chest as he hacked up what felt like an entire lung, despite not having any. Distantly, he could hear Undyne shouting and Alphys’s alarmed cry, but he couldn’t focus well enough to tell what they were saying. Flower after flower forced themselves out past his teeth.

Panic rose within him as more and more flowers were forced up. _no! this isn’t supposed to happen! not here, not now!_

Finally, it was over. Sans gasped and would have fallen face-first in his own magic if two pairs of arms weren’t holding him upright.

“-ans? Sans, are you alright?” That was Undyne.

“D-did we get it wrong? Were we n-not the ones you…” Alphys.

Sans shook his head. “no,” he rasped out. “it’s- it’s you two. it’s always been you two.”

“Then why are you still _doing_ this?” Undyne sounded scared.

Sans opened his mouth to reply, but then he noticed something. The pressure that had built up in his chest the past several weeks was gone. He could breathe clearly, for the first time in over a month.

“i think-” he muttered, and looked up at the faces of two of the monsters he loved most in the Underground. “i think it worked. i don’t feel the flowers anymore.”

Undyne stared at him, mouth open. “They’re gone?” she asked, and Sans grinned at the hope in her voice.

“i think so.”

“C-can I check?” Alphys asked.

Sans turned his smile on her. “‘course, alph.”

With trembling hands, she removed his coat and lifted up his sweater. Sans scrunched his eyes shut, too afraid to watch.

_please be gone please be gone please be-_

What sounded like a choked sob split the air, and Sans opened his eyes to see both women grinning down at him, tears in their eyes. He looked down at his chest. No flowers marred his ribcage. It was free, for the first time since this entire thing began.

Sans barked out a sob of laughter.

A knock sounded on the door, and his brother’s voice echoed through the lab. “I AM BACK.”

Undyne jumped up and raced to unlock the door, throwing it open and dragging him inside. “He’s cured, Papyrus! Sans is _cured!_ ”

“WHA-” Papyrus looked toward Sans and Alphys, and his eyes stopped on Sans’s cleared chest. “THEY’RE GONE,” he said. “THEY ARE TRULY GONE.”

Sans grinned up at his brother. “yeah, boss. they’re gone.”

A grin split Papyrus’s face and he rushed forward, dropping to his knees and flinging his arms around Sans’s neck. “YOU’RE NOT GOING TO DIE,” he whispered.

Sans returned the hug, grin widening at the addition of two more pairs of arms. “i’m not going to die.” Sans laughed, carefree for the first time he could remember. “i’m not going to die!”

\---

Sans stood in the snow outside of Grillby’s, taking deep breaths in the cold air just because he could. It was freeing, breathing without that heavy weight on his chest.

Beside him, Undyne was regaling Alphys of her latest batch of Guards. “...not half bad. Not as good as Papyrus and the dogs, of course, but we can whip them into shape in no time.”

There was a pause, then a hand on Sans’s shoulder startled him out of his thoughts. He turned to see Undyne gazing down at him, eyebrows furrowed.

“Hey, bonehead. You alright?”

Sans grinned up at her and leaned in for a kiss, which she returned immediately. He reached for one of Alphys’s hands.

“i’m good,” he said, smile so wide it felt like it was going to split his face. “never been better.”

**Author's Note:**

> The gladiolus stands for strength, integrity, honor, and infatuation.
> 
> The iris stands for wisdom, knowledge, and trust.


End file.
